Effects Of Interactions Of Zn～(2+) With Catechins On The Prostate Cancer PC-3 Cell Lines

Prostate cancer is one of the most common cancers for men in the world. It has been obviously confirmed that tea could act as a chemoprevention agent for prostate cancer in many animal tumor models and cell culture systems. Epidemiological data also support the premises that dietary intake of tea may reduce the risk of different types of malignancies including cancer of the prostate gland. Tea catechins have showed the exciting results on the reduction of happening of prostate cancer, including inhibition of the proliferation, induction of apoptosis, and regulation of the key enzymes. Zinc ion was indispensable to our health. Moreover, zinc ions played an important role in the normal function and pathology of the prostate gland, and might be a good marker for diagnosing prostate cancer. Many studies have found that cathechins could complex with metal ions and formed stable metal complexes, which had special pharmacological activities. Currently, it has been becoming the focus for the researchers to investigate the interactions of metal ions with catechins extracted from green tea in the field of tea biochemistry and inorganic biochemistry, and Epi-gallocatechin gallate (EGCG) was the major active component in green tea or its extract. However, so far it has not been elucidated clearly in the world how to interact between zinc ion and EGCG, and their behavior in cell biology yet.In the present paper, effects of four mainly tea catechins EGCG, ECG, EGC and EC in tea on the growth of androgen-insensitive (PC-3) human prostate tumor cells were investigated by MTT assay;zinc ions, EGCG and their interactions on the growth of androgen-insensitive prostate cancer cell PC-3 was also studied;Effects of EGCG and Zn²⁺ on absorption of zinc and cadmium in PC-3 cells were detected by Flame Atomic Absorption Spectrometry (FAAS) assay;Effects of Zn²⁺ on the partition coefficients of EGCG in a PBS / n-octanol or water/ n-octanol system were determined by HPLC analysis;EGCG complex with Zn²⁺ and its chemical stability were respectively observed by UV-Vis spectrophotometric assay and HPLC determination.MTT results showed that four catechins found in tea extracts were screened for growth inhibition of PC-3 cells at different degree in dose- and time-dependent manner and they were classified in the order EGCG>ECG>EGC>EC;Zinc ions inhibited the growth of PC-3 cells in a time- and dose-dependently and enhanced the effect of EGCG against PC-3 cells and the interaction of EGCG with zinc ion strongly depended on their concentration and an added order.Flame Atomic Absorption Spectrometry (FAAS) determination confirmed that Zn2+ could increase concentration of zinc and decrease concentration of cadmium in PC-3 cells, and Zn2+ in the presence of EGCG could enhanced such bioactivity in some ways.Partition coefficients analysis showed that Zn2+ increased the Kow value of EGCG in both PBS / n-octanol and water/ n-octanol system in a dose-dependent manner. HPLC separation displayed that EGCG in PBS buffer solution was found to degrade rapidly and completely disappeared after 6 hours;As for EGCG in the presence of Zn2+, the rate of its degradation was slower than EGCG alone. After 12 hours, there was still little EGCG detected, indicating that the stability was increased. Therefore, this finding implied that Zn2+- EGCG complex might strengthen the stability of EGCG and thus kept its bioactivity for longer periods. UV-Vis spectrophotometric assay indicated that the absorption of EGCG in PBS buffer solution (pH 7.0) increased when Zn2+ was added to EGCG solution and the spectra became broader, but the absorption peak didn't shift, which might due to the formation of complex of Zn2+ and EGCG...